Prosthetic knee implantation

ABSTRACT

A prosthetic knee is implanted after cutting the femor and tibia in the proper manner with the aid of instruments which include axial alignment guides and a series of cutting jigs.

Applicant's copending application Ser. No. 684,128, filed Dec. 20, 1984,now abandoned, the details of which are incorporated herein by referencethereto, describes such an anatomically desirable prosthetic kneesystem.

BACKGROUND OF INVENTION

Prosthetic knee components have long been known and used in the art. Inorder to prepare the femor and tibia for the components, it is necessaryto make a series of cuts from these bones to conform to the size andshape of the prosthetic components. Generally these cuts are made byvisual reliance on where the cuts should be sometimes with the aid ofsimplified jigs and/or score lines. Such techniques are necessarilyimprecise which limits the ability to provide the anatomically mostdesirable prosthetic knee.

The aforenoted prosthesis is designed to reproduce anatomic movement ofthe knee without compromising stability. This prosthetic knee, as thenatural knee, provides a "screw home" mechanism which increasesstability in extension. As flexion proceeds, the femoral condylesinitially roll posteriorly. Through asymmetric condylar and tibialcompartments, the natural and changing axes of rotation are preserved,thereby preventing the development of abnormal tension in retainedligaments. When abnormal ligamentous tension develops, it eitherrestricts flexion and increases shear stress at fixation interfacesand/or leads to eventual progressive ligament attenuation and jointinstability. The design also allows natural internal and externalrotation of the knee in flexion. Furthermore, contouring of theposterior margins of the tibial plateaus facilitates stability inflexion and provides a broad contact surface. The combination of thesefactors, which balance soft tissue elements in the joint, minimizesshear stress at the fixation interfaces, enhancing the potential forlong term function of the replaced knee.

In order to make such prosthetic knee system feasible, the necessarybone cuts must be precisely accomplished. This, in turn, requires a setof proper instruments including guides and jigs. Such instruments shouldassure reproducibly accurate bone cuts, prosthetic seating, and lowerlimb alignment.

SUMMARY OF INVENTION

An object of this invention is to provide techniques which permit theabove-noted knee prosthesis to be implanted.

A further object of this invention is to provide instruments includingguides and cutting jigs which assure the necessary accurate bone cuts.

In accordance with this invention, a set of instruments is providedwhich allows for variations in the anatomical axis of the femor. Theinstruments include cutting jigs which are selectively locked directlyto the bone. By use of these instruments, eight basis cone cuts are madeto align and seat the femoral and tibial components of the prosthesis.

THE DRAWINGS

FIG. 1 illustrates the anatomical considerations of the legs which aretaken into account in accordance with the invention;

FIGS. 2a through 2f illustrate the eight basis bone cuts which are madein accordance with the invention;

FIGS. 3-30 illustrate the various steps and instruments used thereinfrom incision to final tibial preparation in the practice of theinvention;

FIGS. 31-35 are side, top, front, bottom and rear views, respectively,of the distal femoral cutting jig shown in FIGS. 7-13;

FIGS. 36-40 are side, front, rear, bottom and plan views, respectively,of the pin holder alignment guide shown in FIGS. 8-9;

FIGS. 41-44 are cross-sectional views taken through FIG. 37 along thelines 41--41, 42--42, 43--43 and 44--44;

FIG. 45 is a front elevation view partly in section of the distalfemoral cutting jig shown in FIGS. 10-13;

FIGS. 46-49 are top, bottom, side and rear views, respectively, of thefemoral cutting jig shown in FIG. 45;

FIG. 50 is a cross-sectional view taken through FIG. 48 along the line50--50;

FIGS. 51-55 are bottom, front, rear, side and top views, respectively,of the femoral drill jig shown in FIGS. 13-14;

FIG. 56 is a cross-sectional view taken through FIG. 52 along the line56--56;

FIGS. 57-61 are top, front, rear, bottom and side views, respectively,of the transverse femoral cutting jig shown in FIGS. 15-16;

FIG. 62 is a cross-sectional view taken through FIG. 57 along the line62--62;

FIG. 63-67 are side, top, front, rear and bottom views, respectively, ofthe femoral spacer/tensor jig shown in FIGS. 17-22;

FIG. 68 is a cross-sectional view taken through FIG. 66 along the line68--68;

FIGS. 69-72 are top, rear, front and bottom elevation views,respectively, of the transverse tibial cutting jig shown in FIGS. 17-23;

FIGS. 73-74 are end elevation views of the transverse tibial cutting jigshown in FIGS. 29-72;

FIG. 75 is a cross-sectional view taken through FIG. 69 along the line75--75;

FIGS. 76-80 are bottom, front, rear, top and end views, respectively, ofthe femoral chamfer cutting jig shown in FIG. 24;

FIG. 81 is a cross-sectional view taken through FIG. 76 along the line81--81;

FIGS. 82-86 are bottom, front, rear, top and end views, respectively, ofa modified form of femoral chamfer cutting jig;

FIG. 87 is a cross-sectional view taken through FIG. 82 along the line87--87;

FIGS. 88-92 are side, top, bottom, front and rear views, respectively,of the tibial positioning/fixation jig shown in FIGS. 25-30;

FIG. 93 is a cross-sectional view taken through FIG. 89 along the line93--93; and

FIG. 94 is a cross-sectional view taken through FIG. 88 along the line94--94.

DETAILED DESCRIPTION

The instruments utilized in the practice of the invention consist oflong axial alignment guides and cutting jigs. The jigs may besequentially numbered relative to their order of use to simplify theprocedure. The alignment guides are designed to assist the surgeon inpositioning all primary cutting jigs prior to making the bone cuts. Allcutting jigs lock onto their respective bones to insure the accuracy ofthe cuts.

The inventive instrument system is designated to seat the femoral andtibial components parallel to the anatomica transverse axis of the knee.Since this axis is parallel to the ground and perpendicular to thevertical in two-legged stance, this positioning achieves: (1) uniformstress distribution at fixation interfaces, (2) optimal alignment; and(3) physiological ligamentous balance of the knee. It is also importantto recognize that the ankles remain closer to the midline vertical axisof the body that either the knee or hips throughout noral gait. Toachieve the goals of total knee arthroplasty, these alignment featuresmust be preserved or reconstituted.

The inventive instrument system uses the femoral shaft axis (S), thecenter of the knee (K), the center of the ankle joint (A), and thetransverse axis of the knee (T) as its alignment references (FIG. 1).The mechanical axis of the lower libm, which runs from the center of thehip (H) through the center of the knee (K) to the center of the ankle(A), generally forms an angle of 3° with the vertical (V), because thehips are wider apart than the ankles in both normal stance and gait(FIG. 1).

Since the femoral head and neck overhang the shaft, the axis of thefemoral shaft does not coincide with that of the leg, but forms with theleg a more acute valgus angle of 6° (SKH, FIG. 1). In total, the femoralshaft axis average 9° of valgus with the vertical. The valgus angle ofthe femur varies relative to body build. The specific femoral valgus fora given individual can be determined by measuring angle HKS (FIG. 1) ona long x-ray which includes both the hip and the knee, and adding 3°(the mechanical axis). This method is valid for reconstituting amechanical axis of 3° regardless of the degree of pre-operative axialdeformity at the knee.

For tibial alignment, the center of the knee and the center of the ankleare used as reference points. Instruments which rely on the proximaltibial shaft as their key alignment reference tend to be inaccurate dueto the frequent occurrence of tibial bowing. Recognizing that the centerof the ankle is closer to the midline vertical axis then the center ofthe knee in two-legged stance and throughout gait, this system uniquelyrequires a small angle at the proximal transverse tibal cut (TKA, FIG.1). This angle keeps the transverse axis of the prosthesis parallel tothe ground while the mechanical axis of the entire lower extremityremains in valgus (HKA, FIG. 1).

FIG. 2 illustrates the eight basis bone cuts required to align and seatthe femoral and tibial components of the prosthesis. As later describedin detail, the instrument system consists of seven sequentially numberedcutting jigs and a femoral/tibial alignment guide. These are designed toinsure the accuracy and alignment of all femoral and tibial bone cuts.

In the practice of the invention, the knee is approached through alongitudinal skin incision, followed by a medical parapatellar capsularincision. The quadriceps tendon is incised longitudinally, allowingeversion and dislocation of the patella laterally (FIG. 3).

Orientation

With the knee flexed to 90°, a 5/16 inch drill hole is made by drill bit10 in the distal femur. It is placed roughly in the center 12 of theintercondylar notch just anterior to the femoral attachment of theposterior cruciate ligament (FIG. 4). The position of this hole 13 (FIG.6) is not critical to the orientation of any femoral bone cuts--it issimply a point of purchase for the distal femoral cutting jig IA. Thelaterally protruding handles 22 are used to rotate the jig so that theposterior rounded eminences parallel to the posterior femoral condylesand the anterior femur is seen as on a sunrise view (FIG. 5). The jig isthen hammered into place. Jig IA includes a pair of locking pins on theside hidden from view in FIG. 5. If there has been significantpreoperative deformity, the short locking pin facing the most prominentcondyle is hammered into place bringing the face of the jig IA flush tothat condyle only.

The Transverse Distal Femoral Cut: Varus-Valgus And Flexion-ExtensionAlignment

The long axial alignment guide 16 is used to establish propervarus-valgus and flexion extension alignment of the distal femoral cuts.The guide pin 18 is positioned into the pin holder in the appropriateright or left 7°, 9° or 11° hole 20 (FIG. 37). This angle is chosenrelative to the pre-operative x-ray measurement technique previouslydescribed in the alignment rationale section. Most often 9° will beappropriate. The guide 16 is then placed into the anterior holes of thedistal femoral cutting jig IA. Correct axial alignment is achieved whenthe long alignment guide pin 18 is parallel to the femoral shaft axis inboth the anterior and lateral views (FIGS. 7 and 8). An examining fingercan be slipped proximally under the quadriceps to get a better idea ofthe direction of the femoral shaft during this alignment procedure. Ifthe alignment pin 18 does not parallel the femoral shaft, a mallet isused to tap the medial handle 20 or lateral handle 22, advancing the jigIA away from the deformed condyle until the axial guide pin 18 parallelsthe femoral shaft (FIG. 9). With the alignment completed, one can easilyvisualize how much bone is missing from the deformed condyle. The IA jigis not stable at this point but must be manually held during insertionand removal of the alignment pinholder and also while placing the IBjig.

A short alignment pin is available to facilitate alignment in twospecial circumstances. The shorter pin avoids impingement with thetorniquet on an obese thigh or with the abdomen of a short patient.

Locking The Distal Femoral Cutting Jig In Position

The axial alignment guide 16 is removed and the tongue of the distalfemoral cutting jig IA and jig IB is slid into the first part of thedistal femoral jig IA (FIG. 10). With the teeth of the IB jig restinglightly on the anterior femur, recheck the alignment for bothvarus-valgus and flexion-extension prior to hammering it in place. Whenproper alignment is assured, first gently tap the IB jig with a malletso that the teeth engage the bone without sliding down an obliquesurface, thereby changing alignment. Then remove the alignment guide andhammer the IB jig firmly in place. There are also drill holes in thecutting bar of the IB jig through which 1/8 inch drill pins can bepassed into the condyles if additional stability is necessary.

Final position of the distal femoral cutting jig IA is rechecked withthe alignment guide. Measure twice, cut once (FIG. 12).

Cutting The Distal Femur

Once the distal femoral cutting jig IA is locked on to the femur, thesurgeon is free to direct his full attention to the cutting of thedistal condyles. Pistol grip, end-cutting oscillating saws are mosteffective for these cuts. It is important that the surgeon pay strictattention to maintaining the saw blade flat against the proximal cuttingsurface of the jig in order to achieve a precise cut (FIG. 13). Careshould be taken to avoid the central intramedullary fixation peg of thejig. Following the initial transverse cut, the saw blade is passed backand forth across the cutting bar to shave the condylar cuts level withthe plane of the cutting jig. This step is important since the saw bladetends to scive away from the desired plane, particularly in moresclerotic bone and toward the deeper portions of the cut. The jigs arenow removed and the distal femoral cuts are completed. In completingthese cuts, the anterior aspect of the distal femoral cut will serve asthe "cutting block" for the remaining posterior aspect. It is,therefore, important that the saw blade be inserted to the full depth ofthe initial cut before the oscillation is started. Otherwise, one runsthe risk of starting a new plane. Once the posterior part has beencompleted, the broadest blade should be passed over the surface to besure that the cut is a single-flat plane. This can also be checked witha cutting block.

Femoral Component Rotational, Medial-Lateral And Anterior-PosteriorAlignment

Rotational, medial-lateral and anterior-posterior orientation of thefemoral prosthesis is determined by the femoral drill jig II. This jighas two posterior skids 24 which are slid between the posterior femoralcondyles and tibial plateaus. These skids automatically position theinstrument in 0° of rotation relative to the coronal plane of the distalfemur (A,A, FIG. 14). The jig should first be centered in themedial-lateral position on the flat cut distal femoral surface, ignoringthe initial keying hole for the IA jig. The jig II is now hammered flushwith the flat surface of the distal femoral condyles. The jig's anteriorprojection contains two holes 26 marked respectively for right and leftknees. When a 1/8 inch drill pin 28, placed in the appropriate hole, isaligned with the center of the patello-femoral groove, correctmedial-lateral and rotational positioning is assured (B, B, FIG. 14).When correct positioning has been assured, a 5/16 inch drill 30 is usedto make the holes for the femoral prosthesis fixation studs (C,C, FIG.14).

Anterior And Posterior Femoral Cuts

Following the removal of the drill jig II, the two 5/16 inch lockingstuds 32 of the anterior-posterior femoral cutting jig III, are insertedinto the distal femoral fixation holes. The jig III is hammered flushwith the flat cut surface of the distal femoral condyles. The anteriorplane of the cutting jig should intersect the anterior cortex of thefemur at the proximal margin of the patellar facets (FIG. 15). If thisplane appears too deep or too anterior, the next most appropriate sizejig should be chosen. If there is any question of which size jig is tobe used, always start with the larger jig. The anterior and posteriorfemoral bone cuts are now completed (FIG. 16). Once again, care must betaken to rest the saw blade flush against the flat surface of the jig.With the posterior condyles removed, complete access to the posteriorcompartment allows removal of the menisci and anterior cruciateligament. The tibial attachment of the posterior cruciate is identifiedand carefully avoided during the next step. Also, all remaining marginalosteophytes on the tibia and femur must be removed so they do notshorten or constrict ligaments or block full extension.

Tibial Alignment And Cuts

The femoral spacer/tensor jig IV and transverse tibial cutting jig V arenow assembled and positioned. The mortise cut out 34 in the transversetibial cutting jig V is slipped over the tongue 36 of the femoralspacer/tensor jig and slid as far proximally as it will go (FIG. 17).Following insertion of the jig's studs into the femoral fixation holes,the leg is brought into full extension. A folded towel or sheet isplaced behind the knee to prevent inadvertent hyperextension at thisstage of the procedure. Next the axial alignment guide 16 with both itsfemoral and tibial alignment pins in place is positioned into thefemoral spacer/tensor jig IV (FIG. 18).

Axial And Rotational Alignment

To achieve correct tibial axial alignment prior to making the transversetibial cut, longitudinal traction and manipulation are applied from thefoot. The goal is to bring the center of the ankle joint directly underthe distal dip of the alignment pin. This alignment will produce aslight tibial angle of 2.5° (A, FIG. 19). Anatomically, the centers ofthe ankle joints are closer together than the centers of the kneejoints. Overall leg alignment will still be in valgus. Correct extensionalignment is achieved when the tibial shaft parallels the alignment pinwhen viewed from the side. Rotational alignment is correct when themedial malleolus is approximately 30° anterior to the lateral malleousin the coronal plane (B, FIG. 19).

If correct axial alignment cannot be achieved at this point with the jigIV is place, then one of the special techniques for dealing with thesevere deformity will have to be employed. The jig V cannot be lockedonto the tibia until correct alignment is achieved.

Soft Tissue/Joint Tension/Alignment

Soft tissue stability is established following initial manual tibialaxial alignment. Each side of the femoral spacer/tensor jig IV hasexpandable arms 38 which spread when its appropriate thumb screw 40 istightened (FIG. 20). The tensor arms are extended to stabilize the jointin the correct alignment. Do not overtighten the femoral spacer/tensorjig IV. The transverse tibial cutting jig V, pushed as far proximally asit will go ensures that only the minimal amount of the tibial plateauswill be removed. When one plateau is considerably more depressed thanthe other, the transverse cutting jig should be slid distally so thatthe plane of the tibial cut will remove enough bone from the depressedplateau to provide a sufficiently flat surface for seating the tibialprosthesis.

Check Of Overall Alignment

Prior to locking the transverse tibial cutting jig V in place, overalllower limb alignment should be checked. For correct alignment, thefemoral alignment pin 18 will parallel the femoral shaft in both theanterior and lateral planes. The tibial alignment pin 19 will extendfrom the center of the knee to the center of the ankle and be parallelto the tibial shaft, in the lateral plane. Rotation is correct when themedial malleolus is approximately 30° anterior to the lateral malleolus(FIG. 19).

The Transverse Tibial Cut

While still under visual control of the axial alignment guide pins 18,19, the transverse tibial cutting jig V is locked in place by drillingtwo 1/8 inch pins through the appropriate holes in the jig (FIG. 21).The alignment guide 16 is now removed and tension is removed from thejig IV by loosening the thumb screws 40. As the knee is flexed to 90°,the femoral spacer/tensor jig IV will pull out of its anchoring holes inthe femur. The jig IV is then slipped proximally, disengaging it fromthe tibial cutting jig V (FIG. 22). The transverse tibial plateau cut isthen made by resting the saw blade flush against the broad flat surfaceof the cutting jig V (FIG. 23). The cut is made as deeply as the sawblade will allow, while care is taken to protect collateral ligaments.Once again, following the initial cut of the oscillating saw bladeshould be run back and forth across the flat surface of the transversecutting jig to shave off any prominent bone that may be left posteriorlydue to sciving of the saw blade in sclerotic bone. The jig V is thenslipped off the locking pins and the cut is completed, making sure thatthe posterior rims of the plateaus are level with the plane of thetransverse cut. Additional care should be taken to preserve theposterior cruciate ligament. Since the transverse tibial cut is madeparallel to the ground for optimal stress distribution as the prosthesisbond interface and because the normal tibial plateau slopes 7° to 10°posteriorly, more bone will be removed anteriorly than posteriorly.

Femoral Chamfer Cuts

The femoral chamfer cutting jig VI is inserted then into the femoralfixation holes. With the saw blade flush against the jig's cuttingplanes 42, the anterior and posterior cuts are made (FIG. 24). As withother cutting jig, it is important to maintain the saw blade perfectlyflush with the cutting surfaces 42 of the jig to assure precise cuts,otherwise the femoral component will not fully seat.

Tibial Component Rotational, Medial-Lateral And Anterior-PosteriorAlignment

The knee is extended and traction is applied from the foot to open thejoint space. The posterior tabs of the appropriate sized tibialpositioning/fixation jigs VII are hooked behind the cut proximal tibia(FIG. 25). The two posterior tabs 44 of the jig position behind theposterior rims of the tibial plataeu, assuring correct posteriorposition of the tibial prosthesis. The knee is then flexed and the jigVII is centrally positioned. Since the posterior margins of the tibialplateaus are nearly parallel to the tranverse axis of the tibia, theposterior tabs 44 will position the jig in correct rotation. Rotationaland medial-lateral positioning are checked by slipping an axialalignment guide pin 19 through the appropriate right or left alignmenthole in the anterior flange of the jig. The two anterior thumb screws 46of the jig are then lightly tightened, securing the jig in place. Ifalignment is correct, the distal tip of the alignment pin should centerover the ankle joint with the medial malleolus 30° anterior to thelateral malleolus (FIG. 26). If this is not the case, the jig ismanipulated into proper alignment. Rotational malalignment tends to betoward external rotation of the tibia.

An appropriate size tibial trial prosthesis 48 is inserted onto the jig(FIG. 27). The trial femoral prosthesis is then positioned onto thefemur.

Initial Trial Reduction

Range of motion and stability are now tested. If the joint is too lax,the next thickest tibial trial is slipped onto the tibialpositioning/fixation jig VII. Once flexion, rotation and stability aresatisfactory, the overall alignment is checked in full extension (FIGS.28 and 29). The alignment guide is removed, and the knee is flexed to90°. Next, the femoral trial and tibial spacer are removed. Thethickness marked on the tibial trial spacer indicates the thickness ofthe prosthesis to be implanted.

Final Tibial Preparation

When the stemmed tibial prosthesis is being used, the window 50 in thejig VII is used, as a cutting guide. A 1/2 inch osteotome 52 is used toprepare the fixation slot while the jig is still locked onto theproximal tibia (FIG. 30).

For the aforenoted prosthesis resurfacing tibial prosthesis which usesmedial and lateral fixation studs, a 5/16 inch drill 54 is used to makethe stud holes through the drill guides in the jig VII (FIG. 30). Withfixation peg or stud holes completed, the jig is removed. A final checkof the joint is made for posterior loose bodies, and soft tissuedebridement is completed.

Instruments

FIGS. 31-94 illustrate in full scale various instruments used inaccordance with this invention.

FIGS. 31-35 illustrate the distal femoral cutting jig IA which is usedfor achieving axial alignment when used with the axial adjustment guide16. Distal femoral cuts are made when jig IA is used with cut jig IB. Asindicated therein, the upper surface of the central portion 56 of jig IAhas attached thereto a pair of lateral handles 22, 22 while a medialhandle 20 also extends from the front face of central section 56. Apositioning pin 58 is disposed on the rear face of central section 56 aspreviously described. Attaching means are provided on the upper surfaceof the central section 56 for selective attachment of the pin holderalignment guide 16. The attaching means is in the form of a pair ofholes 60, 62 which are of different diameter corresponding to thedifferent diameter locking pins 64, 66 (FIG. 37) of the pin holder 16.In this manner there is assurance that the pin holder can be mounted inonly the correct position.

The rear surface of central section 56 also includes a pair of shortalignment pins 68 as previously described.

A vertical cut-out 70 extends completely through central section 56 forreceiving the tongue 72 (FIG. 45) of the distal femur cutting jig IB. Anadjustable locking screw 74 is movable into cut-out 70 to lock tongue 72in place.

FIGS. 36-44 illustrate the details of pin holder 16 which is used withguide pins 18, 19 (FIG. 19) to assure correct axial alignment throughoutthe surgical procedure. Pin holder 16 is in the form of an elongated barand includes bifurcated pins 64, 66 to complement the holes 60, 62 injig IA. The lower portion of pin holder 16 is provided with a pair ofmirror image tibial holes 76, 76 for selectively receiving tibialalignment pin 19. The holes are angled oppositely each other, aspreviously described, with one holder being for the right knee and theother being for the left knee. Similarly, three sets of holes 78, 80, 82are provided for the femoral alignment pin 18. The holes are disposed atthe most likely angle required such as 7°, 9° and 11° with one set beingfor the right knee and the other for the left knee.

FIGS. 45-50 illustrate the details of distal femoral cutting jig IBwhich is in the form of a plate or bar having a downwardly extendingtongue 72 with non-symmetric cross-section of complementary size andshape to fit within the mortise cut-out 70 of jig IA. Jig IB is used forcutting the distal femoral condyles. Plate 84 includes a pair of femoralsecuring pins 86 for attachment to the femur with two pairs ofpositioning pins 88 spaced inwardly thereof. The upper surface of plate84 is also provided with a pair of non-identical holes 90, 92 forreceiving the locking pins 64, 66 of pin holder 16. Plate 84 is alsoprovided with a generally vertical guide surface 94 on each wing portionthereof to act as a saw cutting guide (see FIG. 13). A pair of verticalholes 96 are provided in plate 84.

FIGS. 51-56 illustrate the femoral cutting jig II which is used todetermine the rotational, medial-lateral and anterior-posteriororientation of the femoral component and allows drilling of holes forprosthesis fixation stud. As shown therein, jig II is in the form of agenerally vertical plate 98 having a flat inner surface 100. A pair ofposterior skids 24 extend outwardly from inner surface 100 at the lowerportion thereof. A pair of drill holes 26 extend through plate 98 aspreviously described. If the posterior condyles are intact, a hole maybe drilled therein through the aid of one of the drill holes 102, 102with holes 102, 102 being inclined for the right and left knee. Plate 98also includes a pair of positioning pins 104 on its inner surface 100.

FIGS. 57-62 illustrate the anterior-posterior cutting jig III. Asindicated therein, jig III is in the form of a bar or plate 106 whichhas a flat vertical surface 108. A pair of distal femoral fixation pins32 extend from surface 108. A generally horizontal lower cutting guidesurface 110 is also provided as well as an upwardly inclined cuttingguide surface 112. A cut-out 114 is located centrally of bar 106.Preferably jig III would come in small, medium and large sizes.

FIGS. 63-68 illustrate the details of femoral spacer/tensor jig IV whichassembles and positions transverse tibial cutting jig V to determinecorrect soft tissue balance and tibial axial and rotational alignmentprior to making the transverse tibial cut. Jig IV comprises a pair ofspaced fixed legs 116 with each leg having a lower vertical section andan inwardly inclined upper section. A transverse bridge member 118 joinsthe fixed legs at the junction of the upper and lower sections. A pairof spaced parallel movable legs 38 generally conform in size and shapeto fixed legs 116 and are hingedly mounted at their ends thereof byhinge connection 102 to their respective movable legs. Adjusting meansin the form of bolts or thumb screws 40 are threadably engaged with andextend through fixed legs 116 into contact with movable legs 38 forcontrolling the spacing or relative positioning of the respective setsof legs. A pair of studs 126 are provided at the lower portion of legs116 while rounded contact surfaces 128 extend away from movable legs 38.Legs 38 may thus be moved so that surfaces 128 contact the tibia. Bridgemember 118 includes outwardly extending tongue 36 which is ofnon-symmetrical cross-section for complementary engagement with mortisecut-out 34 in jig V (FIG. 17). Jig V could then slide in or out ontongue 36 to adjust for the length of cut.

FIGS. 69-75 illustrate transverse tibial cutting jig V which is in theform of a bar 130 having a flat upper cutting guide surface 132 andcut-out 34 for receiving tongue 36 of jig IV. A locking screw 134 ismovable into cut-out 34 to lock tongue 36 in place. A pair of verticaldrill holes 136 also extend through bar 130.

FIGS. 76-81 show one form of a femoral chamfer cutting jig VI which isin the form of a bar 138 having its front face formed in three sectionswhich include a pair of inclined upper and lower cutting guide surfaces42 extending to the upper edge and lower edge of bar 138. Theintermediate surface 140 is generally vertical. A pair of positioningstuds 142 are provided to extend into the same medial alignment holeswhich are utilized by various other jigs.

FIGS. 82-87 show a modified form of jig VI wherein a condylar cut-out144 is provided in the lower guide surface. Preferably jig VI would comein five different sizes varying in size of the cut-out 144 and/or beingsized small, medium or large.

FIGS. 88-94 illustrate the tibial positioning/fixation jig VII. Jig VIIgenerally includes a plate 146 having a lower planar surface 148 fromwhich extend a pair of parallel tabs 44. An osteotome cut-out or window50 is provided in the central portion thereof with an inclined drillhole 150 on each side of cut-out 50. A block 152 is connected to plate146. A pair of vertical alignment holes 154 which are inclined for theright and left knee extend through block 152. Additionally thumb screws46 are threadedly mounted into and extend through block 152 while a pairof non-identical holes 156, 158 are provided in block 152 for receivingthe locking pins 64, 66 of holder 16.

What is claimed is:
 1. A femoral spacer/tensor jig comprising a pair ofspaced parallel fixed legs, each fixed leg having a lower verticalsection and an inwardly inclined upper section, a transverse bridgemember joining said fixed legs together, attaching means secured to saidbridge member, a pair of spaced parallel movable legs, each of saidmovable legs generally conforming in size and shape and hingedly securedto a respectively fixed leg, adjusting means for adjusting the spacingbetween each fixed leg and its respective movable leg, and a studextending away from each fixed leg for insertion into a femoral fixationhole.
 2. The jig of claim 1, in combination therewith, a tranversetibial cutting jib, said transverse tibial cutting jig comprising a barhaving a flat upper cutting guide surface, and complementary attachingmeans securing said transverse tibial cutting jig to said attachingmeans of said femoral spacer/tensor jig.
 3. The combination of claim 2including a rounded tibial contacting surface extending outwardly fromsaid vertical section of each of said fixed legs, securing means on saidbridge member for securement of an axial alignment guide thereto, saidattaching means being an outwardly extending tongue having anon-symmetrical cross section, said complementary adjusting means beinga cut-out in said bar of complementary shape to said tonguecross-section, adjustable locking means selectively securing said bar tosaid tongue, and a pair of vertical drill holes extending through saidbar.
 4. A transverse tibial cutting jig assembly comprising a bar havinga flat upper cutting guide surface, a cut-out extending horizontallythrough said bar of non-symmetrical shape, an adjustable locking pinmovable into said cut-out, a pair of vertical drill holes extendingthrough said bar, each of said drill holes being on a different side ofsaid cut-out, and the lower surface of said bar having an inclinedplanar surface at one edge thereof.